1. Field of the Invention
The present invention relates to a two-stroke internal-combustion engine.
2. Description of the Prior Art
In a two-stroke internal-combustion engine in which the burnt gas in the engine cylinders is scavenged by an air-fuel mixture fed into the engine cylinders from the scavenged port, air and fuel are fully mixed so as to form a uniform air-fuel mixture before they are fed into the engine cylinders. Then the uniformly premixed air-fuel mixture is fed into the engine cylinders, and the burnt gas in the engine cylinders is savenged by the uniformly premixed air-fuel mixture. However, in such a two-stroke internal-combustion engine, when the air-fuel mixture flows into the engine cylinders, part of it escapes into the exhaust passage from the exhaust port. Thus, a large amount of fuel is discharged into the exhaust passage without being burnt, with the result that fuel consumption is increased and the amount of harmful hydrocarbon (HC) components in the exhaust gas is increased.